1. Field of the Invention
The present invention relates to a recording disk drive. In particular, the invention relates to a recording disk drive equipped with a heater for adjusting a clearance between a head and a recording disk at a head slider.
2. Description of Related Art
Currently, data recording apparatuses using various media such as an optical disk, magnetic tape, and a semiconductor memory have been known in the art. In particular, a hard disk drive (HDD) has been widely used as a storage device of a computer. The HDD is an indispensable storage device for current computer systems. The HDD has found widespread application such as a removable memory used in a moving image recording/reproducing apparatus, a car navigation system, a cell phone, or a digital camera, in addition to the computer, due to its outstanding characteristics.
A magnetic disk used for the HDD has plural concentric data tracks, each of which records plural servo data including address information and plural data sectors. Plural data sectors are recorded between the respective servo data. A head element portion of a head slider supported to an oscillating actuator accesses a desired data sector based on address information of the servo data, making it possible to write/read data to/from the data sector.
In order to improve a recording density of the magnetic disk, it is important to reduce the clearance between the head element portion flying over the magnetic disk and the magnetic disk. To that end, some mechanisms for adjusting the clearance have been proposed. One of them includes a heater for a head slider to heat a head element portion with the heater to adjust a clearance (see Japanese Unexamined Patent Application Publication No. 2004-192742). In this specification, this mechanism is referred to as “TFC” (Thermal Flyheight Control). According to the TFC, current is supplied to the heater to generate heat, and protrude the head element portion through thermal expansion. Hence, the clearance between the magnetic disk and the head element portion can be reduced.
If the head slider includes the heater for the TFC, it is important to suppress noise on a heater line pair for supplying a heater current and crosstalk noise on a read signal resulting from the noise. The heater line pair has been known to be susceptible to a noise from a preamplifier.
However, crosstalk noise on the read signal results from not only the noise from the preamplifier but noise transmitted from the magnetic disk to the heater line pair. In addition, it has been found that the noise from the magnetic disk is more likely to incur the crosstalk noise on the read signal than the noise from the preamplifier, in some HDDs.
FIG. 10 shows how a crosstalk noise is superimposed on the read signal due to noise transmitted from the magnetic disk into the heater line pair. In FIG. 10, a head slider 83 includes a heater 832, a read element 833, and a write element 834, which are formed on a slider 831 and insulated from one another by an insulator. The configuration of the elements in FIG. 10 is just for illustrative purpose only and the actual configuration may be different.
Noise generated from a servo-controller spindle motor 81 is transmitted to the slider 831 of the head slider 83 via a capacitance component Csm. The noise is transmitted to a suspension via a capacitance component Css and also into a heater line 841 grounded to the suspension via a capacitance component Cha.
The noise is superimposed on the read signal via capacitance components Cra and Crb in the head slider 83. Further, crosstalk occurs between read lines 842a and 842b for supplying a heater current to lower the S/N ratio of the read signal.